Purpose: To investigate muscle deoxygenation and neural drive-related changes during repeated cycling sprints in a fatiguing context.
Methods: Nine healthy male subjects performed a repeated-sprint test (consisting of 10 × 6-s maximal sprints interspaced by 30 s of recovery). Oxygen uptake was measured breath-by-breath; muscle deoxygenation of the vastus lateralis was assessed continuously using the near-infrared spectroscopy technique. Surface electromyograms (RMS) of both vastus lateralis and biceps femoris were also recorded. Furthermore, before and after the repeated-sprint test, the percentage of muscle activation by voluntary drive (twitch-interpolated method) was measured during a maximal voluntary contraction.
Results and Discussion: Consistent with previous research, our data showed a significant power decrement during repeated-sprint exercise. There was also a progressive muscle deoxygenation, but our data showed that the ability of the subjects to use available O2 throughout the entire repeated-sprint test was well preserved. Our data displayed a significant decrement in the RMS activity during the acceleration phase of each sprint across the repeated-sprint exercise. Moreover, decrement in motor drive was confirmed after exercise by a significant decrease in both percentage of voluntary activation and RMS/M-wave ratio during a maximal voluntary contraction.
Conclusion: In this experimental design, our findings suggest that the ability to repeat short-duration (6 s) sprints was associated with the occurrence of both peripheral and central fatigue.
1Motor Efficiency and Deficiency Laboratory, Montpellier, FRANCE; and 2Team Sport Research Group, School of Human Movement and Exercise Science, The University of Western Australia, Crawley, AUSTRALIA
Address for correspondence: Sébastien Racinais, Université de Montpellier 1, Faculté des Sciences du Sports, Laboratoire EA 2991 Efficience et Déficience Motrices, 700 Avenue du Pic Saint Loup, 34090 Montpellier, France; E-mail: firstname.lastname@example.org.
Submitted for publication May 2006.
Accepted for publication September 2006.